A 21nV/√Hz chopper-stabilized multipath current-feedback instrumentation amplifier with 2µV offset

Amplifiers with low offset and low 1/f noise usually employ auto-zeroing (AZ) and/or chopping. However, AZ suffers from noise aliasing, and so requires more power dissipation for a given noise specification. Chopping, although free of noise aliasing, requires notch filters [1, 2] or AZ [3] to remove the ripple caused by up-modulated offset and 1/f noise. This paper describes a chopper-stabilized multi-path current-feedback instrumentation amplifier (CFIA), whose ripple is removed by a continuous-time (CT) ripple-reduction loop (RRL) [2]. In contrast to [2], the notch created by the RRL is eliminated by the use of a multi-path architecture. This results in a CFIA with a smooth single-pole response, which also achieves low offset (2µV) and low noise (21nV/√Hz) in a power efficient manner (NEF=9.6). By appropriately connecting its inputs, the CFIA can also be used as an opamp. In this configuration, its offset is further reduced while its noise and NEF are halved.